Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$85.27	12.838%	$96.217	$96.22	$96.20	$96.20
Purchase #2	$138.97	8.764%	$151.1493	$151.15	$151.15	$151.10
Purchase #3	$159.90	8.229%	$173.0582	$173.06	$173.05	$173.10
Purchase #4	$163.45	10.506%	$180.6221	$180.62	$180.60	$180.60
Purchase #5	$117.91	8.410%	$127.8262	$127.83	$127.85	$127.80
Purchase #6	$89.66	5.131%	$94.2605	$94.26	$94.25	$94.30
Purchase #7	$15.40	3.203%	$15.8933	$15.89	$15.90	$15.90
7 purchase totals =	$770.56		$839.0266	$839.03	$839.00	$839.00